Staphylococcal species are commonly isolated from blood cultures, and many species are known as important pathogens. Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA), is a virulent pathogen isolated from blood cultures in hospitals around the world (Deresinski, S. (2005) Clin. Infect. Dis. 40:562-73.8). Staphylococcus epidermidis and other coagulase-negative staphylococci (CoNS) are common members of the normal flora of skin and recognized as frequent contaminants in blood cultures. The incidence of infections caused by CoNS has increased throughout the world, however, making it increasingly more important to identify and differentiate between potentially pathogenic staphylococcal species and possible skin contaminants in a timely manner for a prompt clinical intervention.
One important pathogenic CONS staph species is Staphylococcus lugdunensis (Freney, J. et al (1988) Int. J. Syst. Bacteriol. 38: 1.68-172). Clinical manifestations of infection with this organism include abscesses, meningitis, ventriculoperitoneal shunt infection, spondylodiscitis, prosthetic joint infection, catheter-related bacteremia, and endocarditis (Castro, J. G., and L. Dowdy (1999) Clin. Infect. Dis. 28:681-2; Pareja, J., et al (1998) Ann. Intern. Med. 128:603-4; Patel, R. et al (2000) J. Clin. Microbiol. 38:4262-3.). The invention provides an isolated biologically pure culture of Staphylococcus pseudolugdunensis, a sample of the culture having been deposited as ATCC accession number PT A-7961. The invention also provides an isolated polynucleotide comprising at least about 200 contiguous residues of SEQ ID NO: 1 or of SEQ ID NO: 2, and may also comprise an isolated polynucleotide comprising at least about 300 contiguous residues of SEQ ID NO: 1 or SEQ ID NO: 2, or an isolated polynucleotide comprising at least about 400 contiguous residues of SEQ ID NO: 1 or SEQ ID NO: 2. In some embodiments, misdated polynucleotide comprising at least about 200 contiguous residues of SEQ ID NO: 1 may comprise a polynucleotide comprising residues from nucleotide position 660 to nucleotide position 858. Isolated polynucleotides of the invention may also comprise those that hybridize under moderately stringent conditions to SEQ ID NO: 1 or SEQ ID NO: 2.
Also provided by the invention is a method for distinguishing Staphylococcus pseudolugdunensis from Staphylococcus lugdunensis isolated from a clinical specimen, or for identifying an unknown bacterial strain from a clinical isolate as Staphylococcus pseudolugdunensis, the method comprising comparing the nucleotide sequence of at least 200 contiguous base pairs of SEQ ID NO: 1 with the nucleotide sequence of a corresponding region of the tuf gene sequence of an unknown bacterial strain, wherein the unknown bacterial strain can be determined to be S. pseudolugdunensis if it demonstrates an at least about 97% sequence identity, and more preferably at least about 99% sequence identity, with the corresponding at least about 200 base pairs of SEQ ID NO: 1. In one embodiment of a method of the invention, the at least about 200 base pairs of SEQ ID NO: 1 include nucleotide sequences corresponding to contiguous sequences including nucleotide positions 660-858 of SEQ ID NO: 1.